code: def test_shift(self):
      # GH 9416
      cat = Categorical(["a", "b", "c", "d", "a"])
  
      # shift forward
      sp1 = cat.shift(1)
      xp1 = Categorical([np.nan, "a", "b", "c", "d"])
      tm.assert_categorical_equal(sp1, xp1)
      tm.assert_categorical_equal(cat[:-1], sp1[1:])
  
      # shift back
      sn2 = cat.shift(-2)
      xp2 = Categorical(
          ["c", "d", "a", np.nan, np.nan],
          categories=["a", "b", "c", "d"],
      )
      tm.assert_categorical_equal(sn2, xp2)
      tm.assert_categorical_equal(cat[2:], sn2[:-2])
  
      # shift by zero
      tm.assert_categorical_equal(cat, cat.shift(0))
  
imports: import re
  import sys
  import numpy
  import pytest
  from pandas.compat import PYPY
  from pandas import Categorical, CategoricalDtype, DataFrame, Index, NaT, Series, date_range
  import pandas._testing
  from pandas.api.types import is_scalar
label_desc: Use image node_id 15 for calling the TestCategoricalAnalytics obj's underlying member method code with example usage: obj.test_shift() without return types